Intercalation of natural flake graphites

Abstract

Natural flake graphites are characterized in terms of their ability to form intercalation compounds. Factors such as amounts and distribution of mineral matter, extents of intercalation by bisulphate and bromine, flake thickness and fissuring which control extents of intercalation are examined. Differences in stabilities of intercalates in the natural flake graphites are assessed. Techniques used to examine the flake graphites include image analysis to assess flake thickness and the degree of fissuring as well as bromine intercalation and desorption as an indication of crystal perfection in flake graphites. Amounts of mineral matter in the flakes and the amount and distribution of crystalline sulphur (not previously reported) in the intercalated flake graphites are studied using EDAX. The intercalated graphites were exfoliated at 1200° C and examined by SEM to assess their extent of expansion and the structure and extent of pinning within the graphite flakes. Results indicate that flake thickness is a primary factor influencing extents of intercalation in these materials, the optimum thickness for bromine intercalation being 25μm. Bromine uptake could indicate the perfection of stacking within a graphite. Mineral impurity in the graphite flake is of importance as it influences flake thickness and cleavage properties.